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The C3a, C4a and C5a components are referred to as anaphylatoxins: [4] [5] they cause smooth muscle contraction, vasodilation, histamine release from mast cells, and enhanced vascular permeability. [5] They also mediate chemotaxis, inflammation, and generation of cytotoxic oxygen radicals. [5]
Cutaneous signs of histamine release are the "flare and wheal"-reaction. The bump and redness immediately following a mosquito bite are a good example of this reaction, which occurs seconds after challenge of the mast cell by an allergen. [7] The other physiologic activities of mast cells are much less-understood.
By 1913 the name histamine was in use, using combining forms of histo-+ amine, yielding "tissue amine". "H substance" or "substance H" are occasionally used in medical literature for histamine or a hypothetical histamine-like diffusible substance released in allergic reactions of skin and in the responses of tissue to inflammation.
Degranulation is a cellular process that releases antimicrobial, cytotoxic, or other molecules from secretory vesicles called granules found inside some cells. It is used by several different cells involved in the immune system , including granulocytes ( neutrophils , basophils , eosinophils , and mast cells ).
Leukocytosis is often seen during inflammation induced by infection, where it results in a large increase in the amount of leukocytes in the blood, especially immature cells. Leukocyte numbers usually increase to between 15 000 and 20 000 cells per microliter, but extreme cases can see it approach 100 000 cells per microliter. [ 9 ]
Histamine is a weak base (a compound able to react with a hydrogen ion to form an acid) that can link with acid groups within the granules of the mast cells. [8] The mechanism of the displacement theory. The crux of this theory lies in the assumption that histamine liberators release histamine by displacing it from cells.
IgE that can specifically recognise an allergen (typically this is a protein, such as dust mite Der p 1, cat Fel d 1, grass or ragweed pollen, food protein, etc.) has a unique long-lived interaction with its high-affinity receptor FcεRI so that basophils and mast cells, capable of mediating inflammatory reactions, become "primed", ready to ...
Mast cells secrete it during the anaphylactic reaction, inducing inflammation. [1] It can be found in basophils. It induces prolonged, slow contraction of smooth muscle and has a major bronchoconstrictor role in asthma. [2] Compared to histamine, it is approximately 1000 times more potent and has a slower onset but longer duration of action.